add function to check if view is empty
add function to check if view is empty

georgepar/rosdep,spaghetti-/rosdep,alessandro-aglietti/rosdep,ros-infrastructure/rosdep,allenh1/rosdep,aymanim/rosdep,sorki/rosdep,sorki/rosdep,allenh1/rosdep,ros-infrastructure/rosdep,wkentaro/rosdep,georgepar/rosdep,alessandro-aglietti/rosdep,spaghetti-/rosdep,aymanim/rosdep,wkentaro/rosdep